The new Sennheiser HD 4.40 BT offers high-quality wireless sound for every day listening on the move. The closed-back, around-ear headset features Bluetooth 4.0 and aptX compatibility to deliver true Hi-Fi sound with satisfyingly dynamic bass. Its elegantly minimalistic design has been crafted from robust, high-quality materials to meet the requirements of the street. The closed-backed design of this headset is fitted with proprietary Sennheiser drivers that came a long way before being allowed to transmit sound to your ears. So, enjoy their well-balanced, amazingly detailed sound with dynamic bass.